This invention relates to a process of preparing para substituted phenylamines from phenylhydroxylamine and nucleophilic reagents, such as amines and alcohols. p-Phenylenediamines, and more specifically, p-aminodiphenylamine are illustrative of the para substituted phenylamines formed in the process of this invention.
Para substituted phenylamines find a variety of utilities depending upon the para substituent. As an example, p-aminodiphenylamine is an important intermediate in the synthesis of rubber antioxidants and antiozonants. Phenylenediamines, particularly C.sub.5-10 alkyl-substituted derivatives thereof, are also useful in stabilizing rubbers. Para aminophenyl alcohols are useful as chemical intermediates. For example, p-hydroxyaniline is employed in the manufacture of analgesics and antipyretics. Other para substituted phenylamines, such as p-chloroaniline, are useful in the manufacture of dyes, medicinals, and resins.
The syntheses of para substituted phenylamines vary depending upon the para substituent and often require several steps which add undesirably to the production costs.
It is known that phenylhydroxylamine reacts with nucleophilic reagents in the presence of aqueous inorganic acids to yield para substituted phenylamines. See, for example, H. E. Heller et al., Nature, 168, 1951) 909, and E. Bamberger, Justus Liebig's Annalen der Chemie, 390, 139-144 (1912); Ibid., 424, 243-245, 294-296 (1921). It is disclosed in these references that phenylhydroxylamine is converted to p-hydroxyaniline in the presence of dilute aqueous sulfuric acid. It is further taught that phenylhydroxylamine reacts with aniline in the presence of dilute aqueous sulfuric acid to yield p-aminodiphenylamine. It is also disclosed that phenylhydroxylamine is converted to o- and p-chloroaniline when the acid employed is hydrochloric acid. Disadvantageously, Bamberger describes multiple by-products, including benzidine, azoxybenzene, and aniline. In a practical sense, there is an added disadvantage. Separation of the acid from the product stream can be expensive. The acid must be neutralized creating a waste salt stream which must be disposed.
It would be advantageous to have a general, one-step process to produce para substituted phenylamines. It would be more advantageous if the process did not require an acid which must be neutralized. Such a process would eliminate the need to dispose of a waste salt stream. It would also be advantageous if high yields of para substituted phenylamines could be obtained. With one or more of these advantages the process would be amenable to commercial application.